Just some minor mouse navigation niggles...
Basically, I don't see the need for a mod key when using the mouse to navigate in the 3D Preview or the Network View. Maybe I'm missing something (if so please set me straight

) but it seems redundant.
3D Preview:LMB - tumble
LMB on a selectable object - select
MMB - pan or zoom
RMB - pan or zoom
When the cursor is over a selectable viewport object, then I can see how a mod key might be useful for supressing its selection - or perhaps you could go the other way and use a mod key (+LMB) for selection and keep navigation strictly no-mod key... whichever.
Network View:LMB (click or drag) - select
MMB - pan or zoom
RMB drag - pan or zoom
RMB click quick-release or click hold with no movement - context menu (See Houdini 9)
There should be a preference setting for whether the MMB or the RMB get assigned to the pan or zoom - personally I prefer MMB for pan and RMB for zoom - just to be picky... but that's the point of a preference.

I guess development is pretty much locked down until TG2 is out of the door, so these suggestions (assuming you like them) are meant for sometime in the future once the pressure has eased a little - though to be honest from what little programming knowledge I have they shouldn't be rocket science to implement - but like I said, what do I know... I bet you guy's have a stack of things waiting to be addressed.
Cheers